A. Field of the Invention
The present invention relates generally to vicinal diol containing monomers and polymers. More specifically, this invention provides monomers and polymers containing vicinal diol groups, methods of preparing such monomers and polymers and high viscosity, high temperature stable aqueous gels formed with the polymers which are particularly useful in treating subterranean formations.
B. Description of the Prior Art
Gelled aqueous fluids are used in a variety of industrial applications to bring about desired results. For example, in the oil industry, gelled aqueous fluids are commonly utilized in carrying out completion, various production stimulation, enhanced production, conformance control and other treatments in subterranean formations containing hydrocarbons. Such gelled aqueous fluids have included both naturally occurring and synthetic water soluble polymer gelling agents as well as agents which cause the polymers to crosslink. The term "aqueous fluid" is used herein to mean any fluid containing some water. The fluid can also contain other components such as alcohols, acids, salts and other miscible or partially miscible substances, gasifiable components such as CO.sub.2 and Na.sub.2, and solids.
The naturally occurring polymer gelling agents utilized heretofore include solvatable polysaccharides such as galactomannan gums, glucomannan gums and cellulose derivatives. The synthetic polymer gelling agents include polyacrylate, polymethacrylate, acrylamide-acrylate copolymers, and others. The crosslinking agents utilized include compounds containing multivalent metals which are capable of releasing metal ions in an aqueous fluid such as multivalent metal salts. Examples of the multivalent metal ions are chromium, zirconium, antimony, titanium, iron, tin, zinc and aluminum.
While the heretofore utilized gelled aqueous fluids have been effective at temperatures below about 180.degree. F., at temperatures above about 200.degree. F., and particularly where the aqueous fluids are brines or otherwise contain calcium ions, such gelled aqueous fluids are unstable in that they precipitate or rapidly degrade and revert to thin fluids. Since many subterranean formations requiring procedures or treatments utilizing gelled aqueous fluids exist at temperatures above about 200.degree. F., there is a need for gelled aqueous fluids which are stable at such high temperatures. The terms "stable at high temperatures" and "high temperature stability" are used herein with respect to gelled aqueous fluids to mean that the gelled aqueous fluids retain substantial viscosity for times greater than about 6 to 8 hours at temperatures in the range of from about 180.degree. F. to in excess of 300.degree. F.
By the present invention, monomers containing vicinal diol groups, polymers formed therefrom and high viscosity gelled aqueous fluids formed with such polymers which are stable at high temperatures are provided.